JP2023043395A - Multiaxial fiber base material, and fiber-reinforced resin molding using the same - Google Patents

Abstract

To provide a multiaxial fiber base material good in impregnation property and impregnation rate of resin when molding, and a fiber-reinforced resin molding molded using the same.SOLUTION: The present invention in one embodiment is a multiaxial fiber base material including: a reinforcing fiber layer arranged with carbon fiber bundles 7 in parallel; and auxiliary fiber layers arranged with auxiliary fibers 8, 9 other than the carbon fiber by angles different from a longitudinal direction of the carbon fiber bundles 7, where the carbon fiber bundles 7 and the auxiliary fibers 8, 9 are integrated by stitch yarns 4, and the stitch yarn 4 is a twisted yarn of a plurality of multifilament yarns having crimp.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD The present invention relates to a multiaxial fiber base material and a reinforcing fiber resin molding using the same.

Carbon fiber, which is a reinforcing fiber material, is compounded with various matrix resins, and the obtained carbon fiber reinforced plastics have come to be widely used in various fields and applications. Because carbon fiber reinforced plastics have high mechanical properties and impact resistance, they are also used in general industrial fields such as the aerospace field, sports applications, automobiles, and wind turbine blades. Carbon fibers have high specific strength and high specific elastic modulus, and a composite material obtained by combining a multiaxial fiber base material containing carbon fiber bundles with a matrix resin is excellent in strength and light weight. As a molding method for this composite material, since the thermosetting resin is impregnated into the multiaxial fiber base material, the highly productive resin transfer molding method (RTM method) and the vacuum assisted resin transfer molding method in which molding is performed in a vacuum state are used. method (VaRTM method) and the like. Impregnability and impregnation speed are important in molding due to the characteristics of thermosetting resin. Insufficient impregnation results in reduced strength, and low impregnation speed results in defective products.

In Patent Document 1, even if thick carbon fiber yarns with low manufacturing cost are used, the yarn width is such that the carbon fiber yarns are arranged uniformly without gaps between the carbon fiber yarns. Techniques have been proposed for improving moldability by expanding the pitch and reducing the thickness of the multiaxial fiber base material.
Patent Literature 2 proposes a technique for accurately and stably controlling a fiber bundle to a target width by drawing, with the aim of obtaining a composite material with good impregnation of a matrix resin and excellent mechanical properties with good productivity. there is
In Patent Document 3, in order to improve the impregnation property when a multiaxial fiber base material is impregnated with a matrix resin to produce a carbon fiber reinforced composite material, the fineness of the carbon fiber single fiber is set to 1.2 to 2.4 dtex. , discloses a multiaxial fiber base material in which the lamination angle of sheets in which carbon fiber threads are arranged in parallel is controlled.

International Publication WO 01/063033 JP-A-2004-256961 JP 2014-163016 A

However, when the fiber volume ratio (Vf) in the reinforcing fiber resin molded article molded using the multiaxial fiber base material is high and the multiaxial fiber base material is long, the resin impregnation property and impregnation speed are reduced. There is a problem and further improvement is required.

The present invention provides a multiaxial fiber base material having good resin impregnation property and impregnation speed during molding, and a reinforcing fiber resin molded article molded using the same.

In one aspect of the present invention, a reinforcing fiber layer in which carbon fiber bundles are arranged in parallel, and an auxiliary fiber layer in which auxiliary fibers other than carbon fibers are arranged at an angle different from the longitudinal direction of the carbon fiber bundles. wherein the carbon fiber bundle and the auxiliary fibers are integrated with a stitch yarn, wherein the stitch yarn is a twisted yarn of a plurality of crimped multifilament yarns. It relates to an axial fiber base material.

In one aspect, the present invention relates to a reinforcing fiber resin molded article in which the multiaxial fiber base material of the present invention is impregnated with a thermosetting resin.

The multiaxial fiber base material of the present disclosure uses twisted yarns of multiple multifilament yarns having crimps as stitch yarns for integrating carbon fiber bundles and auxiliary fibers, thereby impregnating resin during molding. Good properties and impregnation rate. That is, the multiaxial fiber base material is easily impregnated with the resin through the stitch yarns, the impregnation rate is increased, and a reinforcing fiber resin molded article having good resin impregnation can be provided.

FIG. 1 is a schematic cross-sectional view of a conjugate fiber (sheath-core type composite fiber) that constitutes a stitch yarn that constitutes a multiaxial fiber base material of one embodiment of the present invention. FIG. 2 is a schematic perspective view of stitch yarns forming the multiaxial fiber base material of one embodiment of the present invention. FIG. 3 is a schematic perspective view of a multiaxial fiber base material of one embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a general VaRTM method. FIG. 5A is a schematic cross-sectional view of a VaRTM device used in one embodiment of the present invention, and FIG. 5B is a schematic plan view of the same. FIG. 6A is a photograph of a cross section cut perpendicular to the longitudinal direction (orientation direction of carbon fiber bundles) of a molded body obtained in an example of the present invention, and FIG. 6B is a trace diagram of the same photograph. be. FIG. 7A is a photograph of a cross section cut along the longitudinal direction of a molded article obtained in an example of the present invention, and FIG. 7B is a trace diagram of the same photograph. FIG. 8 is a graph of a 3-point bending test measured with the tool side down of the compact obtained in one example of the present invention. FIG. 9 is a graph of a three-point bending test measured with the media surface of the compact obtained in one example of the present invention facing down. FIG. 10 is a graph of a tensile test of a compact obtained in one example of the present invention. FIG. 11 is a graph at the time of measurement of crimp rate and residual crimp rate in one example of the present invention.

[Multiaxial fiber base material]
In one aspect of the present invention, a reinforcing fiber layer in which a plurality of carbon fiber bundles are arranged in one direction, and auxiliary fibers other than carbon fibers are arranged at an angle different from the longitudinal direction (orientation direction) of the carbon fiber bundles. A twisted yarn of a plurality of crimped multifilament yarns is used as a stitch yarn for integrating the carbon fiber bundle and the auxiliary fiber.
The carbon fiber bundle is the main reinforcing fiber layer in the multiaxial fiber base material, and it is preferable to use tow-like carbon fibers composed of a large number of carbon fibers. Auxiliary fibers include glass fiber, aramid (including para-type and meta-type) fiber, polyarylate fiber, poly(p-phenylenebenzobisoxale) (PBO) fiber, poly(p-phenylenebenzobisthiazole) (PBZT) Fibers other than carbon fibers are preferred, such as fibers, high molecular weight polyethylene fibers, polyetheretherketone fibers, or polyvinylalcohol fibers. Among these, glass fiber is preferable from the viewpoint of cost, strength, durability, and the like.

The reinforcing fiber layer may be one layer or two or more layers in the multiaxial fiber base material. In the case of two or more layers, the longitudinal directions of carbon fiber bundles in different reinforcing fiber layers may be the same or different. When the multiaxial fiber base material has one or more reinforcing fiber layers, the longitudinal direction (orientation direction) of at least one layer of carbon fiber bundles is the same as the longitudinal direction (MD direction) of the multiaxial fiber base material. and preferred.

The auxiliary fiber layer in which the auxiliary fibers are arranged at an angle different from the longitudinal direction of the carbon fiber bundle may be one layer, or may be two or more layers. The auxiliary fibers are arranged such that their longitudinal direction is at a different angle from the longitudinal direction of the carbon fiber bundle. When there are a plurality of reinforcing fiber layers, the orientation direction of the auxiliary fibers should be different from the longitudinal direction of the carbon fiber bundles of at least one reinforcing fiber layer, but the longitudinal direction of the carbon fiber bundles of any reinforcing fiber layer It is preferable that both are different. For example, when the auxiliary fiber layer is two layers, for example, the longitudinal direction of the carbon fiber bundles of the reference reinforcing fiber layer, which is the same as the longitudinal direction of the multiaxial fiber base material and the carbon fiber bundles, is set to 0 °, the longitudinal direction of the supplementary fibers of one supplementary fiber layer is +60°, and the longitudinal direction of the supplementary fibers of the other supplementary fiber layer is −60°. As another example, when the longitudinal direction of the carbon fiber bundle of the reinforcing fiber layer serving as a reference is 0°, the longitudinal direction of the auxiliary fibers of one auxiliary fiber layer is +45°, and the other auxiliary fiber layer The longitudinal direction of the auxiliary fibers is -45°. The angle relationship between the carbon fiber bundles and the auxiliary fibers can be arbitrary.

The stitch yarn constituting the multiaxial fiber base material of the present invention is a twisted yarn of a plurality of crimped multifilament yarns. As the stitch yarn, a plurality of multifilament yarns are subjected to real twisting and heat setting multiple times, real twisting-secondary twisting yarn, false twisting-secondary twisting yarn, real twisting-false twisting yarn, knit / denit yarn. or a additionally twisted yarn obtained by heat-treating a side-by-side composite yarn or an eccentric conjugate yarn to develop a crimp. Among these, a yarn obtained by repeating real twisting and heat setting a plurality of times is preferable, and a yarn obtained by repeating real twisting and heat setting twice is more preferable. For this yarn, for example, 2 to 10 raw yarns (unprocessed yarn) are aligned, real twisted, heat set at 100 to 150 ° C., real twisted again in the same or opposite direction, and heat set at 100 to 150 ° C. obtained by In addition, a real twist-secondary twist yarn is also preferable, and this yarn is obtained by, for example, arranging 2 to 10 multifilament raw yarns, real twisting them, and re-twisting them in the same direction while heat-treating at 100 to 150 ° C. can get. Each twist number is preferably 180 to 280 times/m, and the twist direction may be either S twist (right) or Z twist (left).

The twist coefficient K of the stitch yarn is preferably in the range of 500 to 20,000, more preferably 1,000 to 15,000, even more preferably 2,000 to 10,000, still more preferably 3,000 to 10,000. The twist coefficient K can be obtained by the following formula.
K = T x D1 ^/2
However, T is the number of twists (twist/m), D is the fineness (decitex)

The crimp rate of the stitch yarn is preferably 1% or more, more preferably 1 to 5%, still more preferably 1.1 to 4%, as measured according to JIS L1015 8.12. The residual crimp ratio is preferably about the same as the crimp ratio. When the crimp rate is within the above range, the bulkiness of the stitch yarn is improved, the resin impregnation property and the impregnation speed during molding are improved, and the stitch yarn is easy to knit. Further, when the crimp rate is within the above range, shrinkage due to stitch yarns of the multiaxial fiber base material is suppressed.

The stitch yarn is a twisted yarn of a plurality of crimped multifilament yarns, and the fineness of a single fiber of the multifilament yarn is preferably 1 to 6 decitex, more preferably 1.5 to 5 decitex, and still more preferably. 2 to 4 decitex. When the fineness of the monofilament is within the above range, the resin is easily impregnated during molding. The total fineness of the stitch yarn is preferably 40-600 decitex, more preferably 100-500 decitex, still more preferably 150-400 decitex. If it is the above, it becomes a stitch thread which is easy to knit.

The stitch yarn is a twisted yarn obtained by twisting a plurality of multifilament yarns, and the number of twisted multifilament yarns is preferably 2 to 10, more preferably 3 to 8, and even more preferably 4 to 6. is. After twisting and bundling multiple multifilament yarns, they are heated and heat set, and then twisted in the same direction to increase bulkiness and create a space for resin to flow, allowing the resin to contain during molding. improves.

The stitch yarn is a core-sheath conjugate yarn (twisted multifilament yarn composed of a core-sheath type composite fiber), and the core component of the core-sheath type composite fiber is a relatively high-melting polymer, Heat-sealable yarns of low melting point polymers are preferred. By using the above-described core-sheath conjugate yarn as the stitch yarn, the sheath is fused to the fibers constituting the reinforcing fiber layer and the auxiliary fiber layer, improving the workability of the multiaxial fiber base material.

The stitch yarn is preferably a polyester heat-sealable conjugate yarn.

The weaving direction of the stitch yarn is preferably the same direction as the longitudinal direction of the carbon fiber bundle of the reinforcing fiber layer serving as the reference, that is, the same direction as the MD direction of the multiaxial fiber base material. It is preferable that the carbon fiber bundles of at least one reinforcing fiber layer are oriented in a direction of 0° with respect to the direction in which the stitch threads extend. The stitch row density is preferably 2-10 rows/inch (2-10 gauge/inch).

It is preferable that the multiaxial fiber base material has its flatness adjusted by hot roll pressure bonding. The temperature of the heating roll is preferably a temperature at which the stitch yarn is not welded, for example, preferably 140 to 180°C, more preferably 150 to 170°C.

[Reinforcing fiber resin molding]
The multiaxial fiber base material is preferably impregnated with a thermosetting resin by a resin transfer molding method (RTM method) or a vacuum assisted resin transfer molding method (VaRTM method) to form a reinforcing fiber resin molding. These methods are preferable because the resin is easily impregnated from the stitch yarn portion of the multiaxial fiber base material. The impregnation and shaping of the thermosetting resin into the multiaxial fiber base material is preferably carried out in a state in which 1 to 200 sheets of the multiaxial fiber base material are laminated, more preferably in a state in which 2 to 200 sheets are laminated. preferable. That is, in one aspect of the present invention, a resin transfer molding method (RTM method) or a vacuum assisted molding method is applied to one multiaxial fiber base material or a laminate in which a plurality of multiaxial fiber base materials are laminated. The present invention relates to a method for producing a reinforcing fiber resin molding, including impregnating a thermosetting resin by a resin transfer molding method (VaRTM method).

Examples of thermosetting resins include epoxy resins, phenol resins, vinyl ester resins, unsaturated polyester resins, cyanate ester resins, bismaleimide resins, and benzoxazine resins. Further, a modified body of each of these resins may be used, or plural kinds of resins may be blended and used. Further, a curing agent, various additives, fillers, coloring agents, etc. may be added to the thermosetting resin.

In the manufacturing method of the reinforcing fiber resin molded article, the molding of the reinforcing fiber resin molded article is preferably performed at room temperature, and in the case of the VaRTM method, the degree of vacuum is preferably about 1 MPa. The fiber volume ratio (Vf) in the reinforcing fiber resin molding is preferably 50 to 60%.

Description will be made below with reference to the drawings. In the following drawings, the same symbols indicate the same items. FIG. 1 is a schematic cross-sectional view of a conjugate fiber (core-sheath type composite fiber) 1 forming a stitch yarn forming a multiaxial fiber base material of one embodiment of the present invention. The conjugate fiber 1 has a core component 2 of polyethylene terephthalate (melting point 256-260°C) and a sheath component 3 of copolyester, and is heat-sealed at about 190°C.

FIG. 2 is a schematic perspective view of stitch yarns constituting the multiaxial fiber base material of one embodiment of the present invention. The stitch yarns shown in FIG. It is a yarn obtained by real-twisting and additional-twisting, obtained by aligning four strands of 5d, real-twisting them, and additionally twisting them again in the same direction while heat-treating them.

FIG. 3 is a schematic perspective view of a multiaxial fiber base material according to one embodiment of the present invention. As shown in Figure 3, the multiaxial fiber substrate 6 of one embodiment of the present invention is a multiaxial insert warp knit. The multiaxial fiber base material 6 includes a reinforcing fiber layer 70 in which a plurality of carbon fiber bundles 7 are arranged in parallel, and auxiliary fiber layers 80 and 90 . The orientation directions of the auxiliary fibers 8 and 9 forming the auxiliary fiber layers 80 and 90 are different from the orientation direction of the carbon fiber bundles 7 respectively. The carbon fiber bundle 7 and the auxiliary fibers 8 and 9 are stitched (bound) in the thickness direction by a stitch thread 4 hooked on a stitch needle 10 to be integrated. In the integration by the stitch thread, the stitch thread is pierced through the laminate of the reinforcing fiber layer 70 and the auxiliary fiber layers 80 and 90 while chain stitching or the like is performed using the stitching needles 10 provided at regular intervals. It is done by letting The degree of tightening of each layer by the stitch thread, the loop interval of the chain stitch, the density of the stitch rows, etc. are set in consideration of the impregnation property and impregnation speed of the thermosetting resin. In this example, when the longitudinal direction of the carbon fiber bundle 7 is 0°, the auxiliary fibers are arranged at +60° and -60° to integrate the whole.

FIG. 4 is a schematic cross-sectional view of a general VaRTM method. In the VaRTM device 11 shown in FIG. 4, a multiaxial fiber base material 13 is placed on a metal plate 12, and a peel ply (release sheet) 14 and a medium (resin diffusion mesh sheet) 15 are placed on the surface thereof. The surface is covered with a packing film 16, the liquid resin is supplied from the resin inlet 17 on the right end, and the liquid resin is moved in the direction of arrow A by vacuuming from the suction port 18 on the left end. Thereby, the liquid resin is impregnated into the multiaxial fiber base material 13 .

The present invention will be specifically described below using examples. In addition, the present invention is not limited to the following examples. The measurement method is as follows.

<Twist factor K>
The twist coefficient K in real twisting (additional twisting) was calculated by the following formula.
K = T x D1 ^/2
However, T is the number of twists (twists/m), and D is decitex.

<Crimp rate and residual crimp rate>
From the length (mm) when an initial load of 0.18 mN × number of tex is applied to the yarn (sample) to be measured and the length (mm) when a load of 4.41 mN × number of tex is applied, The crimp rate (Cp) and residual crimp rate (Cpr) were calculated according to the following equations. The average value of 20 measurements is shown in Table 1 below.
Cp (%) = {(ba)/b} x 100
Cpr (%) = {(bc)/b} x 100
Sample length: 20 mm (grip length: 5 mm x 2 locations)
a: Length when initial load is applied (mm)
b: length (mm) when a load of 4.41 mN x number of tex is applied
c: Length (mm) when the initial load is applied after being left for 120 seconds (standby)
FIG. 11 is a graph showing the measurement of crimp rate and residual crimp rate in one example of the present invention. The vertical axis is test force (mN) and the horizontal axis is time (sec). The above a, b, and c are the values at the time shown in FIG.

(Example 1)
(1) Stitch thread Core component is polyethylene terephthalate (melting point: 256-260°C), sheath component is copolyester (melting point: about 190°C), fineness of single fiber is 2.3 decitex, total fineness is 56 decitex, number of filaments is 24. of conjugated multifilament yarn was used. This yarn is commercially available from KB Seiren Co., Ltd. under the trade name of "Bell Couple". In an atmosphere with a room temperature of 25 to 30°C (adjusted by air conditioning) and a humidity of about 45 to 60% (not humidified, etc.), 4 of these yarns are aligned and real twisted (twisting direction S) at 250 times / m. After the addition, while heat-treating at 140° C. (passing through an atmosphere of 140°), real twist (twisting direction S) of 250 turns/m was again applied to obtain a stitch yarn. The twist factor K was 7485. The obtained stitch yarn was bulkier and rounder than the stitch yarn used in Comparative Examples 1 and 2 below.

(2) Contents of multiaxial fiber base material Materials other than stitch yarns, manufactured by Kurashiki Boseki Co., Ltd., under the trade name of "CF Kuramas UD618" were used. The contents are as follows.
・ Carbon fiber bundle: 50K (manufactured by Mitsubishi Chemical Corporation, product number: TRW40 50), diameter 0.6 mm
・Glass fiber: Fineness 67 tex (manufactured by Nitto Boseki, E glass)

(3) Production of multiaxial fiber base material A multiaxial fiber base material was produced in the following procedure.
・Glass fibers (auxiliary fibers) were arranged in the direction of +60°.
・On the above, glass fibers (auxiliary fibers) were laminated in the -60° direction.
・The carbon fiber bundles were laminated in one direction (UD direction).
・A laminate consisting of two layers of auxiliary fiber layers and reinforcing fiber layers was woven with stitch threads along the longitudinal direction (orientation direction of carbon fiber bundles) to integrate them (Fig. 3). The stitch row density was 5 rows/inch (5 gauge/inch).
- The obtained multiaxial fiber base material was heat-pressed at 150°C using nip rolls in order to adjust the flatness.
・The mass (basis weight) per unit area of the obtained multiaxial fiber base material was 618 g/m ² , the breakdown of which was 585 g/m 2 for carbon fiber (main fiber bundle) and 585 g/m ² for glass fiber (auxiliary fiber bundle). yarn) was 8 g/m ² ×2 formula (+60° and -60°), stitch yarn was 17 g/m ² . The width of the multiaxial fiber base material was 150 mm.

(4) VaRTM Method Molding Using the VaRTM apparatus 19 shown in FIGS. 5A and 5B, a reinforcing fiber resin molding was molded by the VaRTM method. In the VaRTM device 19 used, a multiaxial fiber base material 13 is placed on a metal plate 12 having a length of 400 mm and a width of 150 mm, and a peel ply (release sheet) 14 and media (resin A mesh sheet for diffusion) 15 is placed in this order, the entire surface of the molding surface is covered with a packing film 16, liquid resin is supplied from the resin inlet 17 on the right end, and vacuum is drawn from the suction port 18 on the left end. The liquid resin was moved in the direction of arrow A, thereby impregnating the multiaxial fiber base material 13 with the liquid resin. However, in the VaRTM device 19, the media (reticulated sheet for resin diffusion) 15 is arranged only in a region up to 100 mm from the resin inlet 17 in the direction of the arrow A, hereinafter referred to as "media portion 15").
- In this example, six multiaxial fiber base materials were laminated on the metal plate 12 .
・The six multiaxial fiber substrates were laminated so that the orientation direction of the carbon fiber bundles was the same.
- The multiaxial fiber base material laminated with 6 sheets was placed on the metal plate 12 so as not to overlap with the media part 15 .
- Covered with a backing film from the top to make it airtight. The resin injection part was performed from the media part.
・While vacuuming at 1 MPa, the epoxy resin was injected in two directions of 0° direction and 90° direction with respect to the orientation direction of the carbon fiber bundle.
・The molding temperature was normal temperature (25° C.), and the fiber-reinforced composite material was molded by injecting and impregnating the resin for a certain period of time.
The matrix resin was an epoxy resin manufactured by Guangdong Broadwin under the trade name of "EpoTech".
- The fiber volume ratio (Vf) was set to 55%.

(Example 2)
As the stitch thread, KB Seiren Co., Ltd., trade name "Bellcouple", single fiber fineness is 2.3 decitex, total fineness is 56 decitex, two conjugate multifilament threads with 24 filaments, and single fiber fineness is 3. 5 decitex, total fineness is 84 decitex, one conjugate multifilament yarn with 24 filaments is pulled, 230 times / m real twist (twist direction S) is added, and while heat treatment is performed at 140 ° C., 230 times / A real twist (twisting direction S) of m was applied to obtain a stitch yarn. The twist factor K was 6440. Other than that was carried out in the same manner as in Example 1. The obtained stitch yarn was bulkier and rounder than the stitch yarn used in Comparative Examples 1 and 2 below.

(Comparative example 1)
As a stitch thread, a single fiber fineness of 10.4 decitex, a total fineness of 167 decitex, and a conjugate multifilament thread of 16 filaments (manufactured by KB Seiren Co., Ltd., trade name "Bell Couple") was used. Twisting (twisting direction S) was applied, and while heat-treating at 140° C., real twisting (twisting direction S) was applied again at 230 turns/m to obtain a stitch yarn. The twist factor K was 5943. Other than that was carried out in the same manner as in Example 1.

(Comparative example 2)
As a stitch thread, a single filament fineness of 10.4 decitex, a total fineness of 167 decitex, and a conjugate multifilament thread of 16 filaments (manufactured by KB Seiren Co., Ltd., trade name "Bell Couple") was used as raw silk without twisting. The procedure was carried out in the same manner as in Example 1, except that it was used as is.
The above conditions are summarized in Tables 1 and 2.

含浸速度は、０°方向は３０分以内で合格、９０°方向は７０分以内で合格とした。
含浸性の評価は下記の通り行った。

As for the impregnation speed, the 0° direction within 30 minutes was considered acceptable, and the 90° direction within 70 minutes was considered acceptable.
Evaluation of impregnability was performed as follows.

From Table 2, it can be seen that Examples 1 and 2 are excellent in resin impregnability and impregnation rate.

(Evaluation of compact)
(1) Cross-sectional observation FIG. 6A is a photograph of a cross-section cut in the thickness direction perpendicular to the longitudinal direction (orientation direction of carbon fiber bundles) of the molded article obtained in one example of the present invention, and FIG. 6B. is a trace diagram of the same photograph. Moreover, FIG. 7A is a photograph of a cross section cut along the longitudinal direction of a molded article obtained in an example of the present invention, and FIG. 7B is a trace diagram of the same photograph. As is clear from the photographs of FIGS. 6A and 7A, no voids were observed, and the impregnating property of the resin was good. 6B and 7B, the molded body 20 is composed of a resin-impregnated multiaxial fiber base material portion 21 and a resin portion 22 .

Among the molded bodies of Example 1, the molded body obtained by injecting the resin from the 0° direction with respect to the orientation direction of the carbon fiber bundles was cut so that the length of the carbon fiber bundles was 140 mm. , a sample was prepared and subjected to a three-point bending test under the following conditions.
(2) 3-point bending test Sample: length: 140 mm, width: 15.7 mm, thickness: 3.6 mm
-Conditioning: Allowed to stand still for 48 hours or more in an atmosphere of 23°C temperature and 50% RH relative humidity.
・Test: 3-point bending test (JIS K7074 compliant)
・Equipment: Precision universal testing machine AG-50kNXDplus (manufactured by Shimadzu Corporation)
・Measurement direction: media side (front side), tool side (back side)
・Jig: indenter = R5 (corner roundness 5mm), fulcrum = R2 (corner roundness 2mm)
・Lower support interval: 140mm
・Test speed: 1mm/min
・The number of tests was set to 5, and the average value was calculated.

Table 3 and FIGS. 8 and 9 show the measurement results of the three-point bending test. FIG. 8 is a graph of a three-point bending test measured with the tool surface of the compact obtained in Example 1 facing down, and FIG. 9 shows a three-point bending test measured with the media surface of the same compact facing down. is a graph of Table 3 shows the average values of 5 tests, and the graphs in FIGS. 8 and 9 are the measurement results of the first sample, which do not match perfectly.

From the results in Table 3 and FIGS. 8 and 9, it was confirmed that the properties of the tool surface and the media surface were similar and homogeneous, and therefore the impregnating property of the resin was good.

(3) Tensile test Among the molded bodies of Example 1, the molded body obtained by injecting the resin from the direction of 0° with respect to the orientation direction of the carbon fiber bundles was measured so that the length of the carbon fiber bundles was 250 mm. A sample was prepared by cutting in the following manner, and a tensile test was performed under the following conditions.
・Sample: length 250 mm, width 15 mm, thickness 3.4 mm
-Conditioning: Allowed to stand still for 48 hours or more in an atmosphere of 23°C temperature and 50% RH relative humidity.
・Test: Tensile test, compliant with JIS K7165 ・Equipment: Universal material testing machine 55R-4206 type (Instron)
・Distance between chucks: 150mm
・Test speed: 1mm/min
・Number of tests: 6
Table 4 and FIG. 10 show the measurement results of the tensile test.

From the above results, it was confirmed that the molded articles of the examples of the present invention had no voids and the like, were excellent in impregnability, and had sufficient performance for practical use. It was also confirmed that by using a twisted yarn of a plurality of crimped multifilament yarns as a stitch yarn, the resin solution is easily impregnated and the impregnation speed is high.

Since the multiaxial fiber base material of the present invention has good resin impregnating property and impregnation rate during molding into a molded body, a reinforcing fiber resin molded body molded using this multiaxial fiber base material has molding defects such as voids. The occurrence of is suppressed, for example, it is useful as a fiber reinforcement in fields that require high mechanical properties and impact resistance, such as the aerospace field, sports applications, automobiles, and windmill blades.

1 Conjugate fiber (single fiber) constituting stitch yarn
2 Core component 3 Sheath component 4 Stitch yarns 5a, 5b, 5c, 5d Multifilament yarns 6, 13 Multiaxial fiber base material 7 Carbon fiber bundle 70 Carbon fiber layers 8, 9 Auxiliary fibers 80, 90 Auxiliary fiber layer 10 Needle for stitching 11, 19 VaRTM device 12 Metal plate 13 Multiaxial fiber base material 14 Peel ply (release sheet)
15 media (mesh sheet for resin diffusion)
16 packing film 17 resin inlet 18 suction port 20 molded body 21 resin-impregnated multiaxial fiber base material portion 22 resin portion

Claims (11)

a reinforcing fiber layer in which carbon fiber bundles are arranged in parallel;
an auxiliary fiber layer in which auxiliary fibers are arranged at an angle different from the longitudinal direction of the carbon fiber bundle;
A multiaxial fiber base material in which the carbon fiber bundle and the auxiliary fiber are integrated with stitch yarn,
The multiaxial fiber base material, wherein the stitch yarn is a twisted yarn of a plurality of crimped multifilament yarns. 2. The multiaxial fiber base material according to claim 1, wherein the twist coefficient K of said stitch yarn is in the range of 500-20,000.
Here, the twist coefficient K is obtained by the following formula.
K = T x D1 ^/2
However, T is the number of twists (turns/m) and D is the fineness (decitex). The multiaxial fiber base material according to claim 1 or 2, wherein the stitch yarn has a crimp rate of 1% or more as measured according to JIS L1015 8.12. The multiaxial fiber according to any one of claims 1 to 3, wherein the stitch yarn is a yarn obtained by aligning a plurality of the multifilament yarns, real-twisting them, and additionally twisting them while heat-treating them to develop crimps. Base material. The fineness of the single filament of the filament constituting the stitch yarn is 1 to 6 decitex,
The multiaxial fiber base material according to any one of claims 1 to 4, wherein the stitch yarn has a fineness of 40 to 600 decitex. The multiaxial fiber base material according to any one of claims 1 to 5, wherein the stitch yarn is a twisted yarn of 2 to 10 crimped multifilament yarns. 8. The multiaxial fiber base according to any one of claims 1 to 7, wherein the stitch yarn is composed of a core-sheath conjugate yarn, and the core component is a high-melting polymer and the sheath component is a heat-fusible yarn with a low-melting polymer. material. The multiaxial fiber base material according to any one of claims 1 to 7, wherein the stitch yarn is composed of a polyester heat-sealable conjugate yarn. The multiaxial fiber base material according to any one of claims 1 to 8, wherein the multiaxial fiber base material is flattened by a heating roll. A reinforcing fiber resin molded article, in which the multiaxial fiber base material according to any one of claims 1 to 9 is impregnated with a thermosetting resin. The reinforcing fiber resin molding according to claim 10, impregnated with a thermosetting resin by a resin transfer molding method (RTM method) or a vacuum assisted resin transfer molding method (VaRTM method).

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